The Physics

A New Class of Nuclear Reactor

Engineers and researchers have long dreamed of a self-fueling source of energy. As early as 1958, Saveli Feinberg imagined a nuclear reactor that could breed fuel within its core. TerraPower will use proven fast reactor technology, high-performance computing simulations and real testing in current fast reactor test facilities to make the traveling wave reactor (TWR) concept a reality. The TWR technology is a uniquely designed nuclear reactor. It is able to operate for an extended period of time, using only depleted uranium (U-238) as fuel. This material is produced during the enrichment process, when enriched uranium (U-235) separates from natural uranium. U-235 is the main fuel for today’s light water reactors, while U-238 is a by-product of the enrichment process and is currently set aside as waste. Nuclear power plants produce electricity by splitting large atoms, such as U-235, into smaller atoms. Each time an atom splits (or “fissions”) it releases neutrons and heat. In turn, released neutrons cause other fissions, creating a sustained chain reaction. For conventional nuclear energy plants, U-235 is used because U-238 cannot sustain a chain reaction in today’s light water reactors. TerraPower’s engineers discovered a method to extract energy from U-238, making it a perfect source of energy for the TWR design.

Innovative Core Physics

The TWR technology’s economic benefits stem from its higher thermal efficiency and ability to breed and burn metallic fuel comprised of initial starter fuel of U-235 and U-238. TerraPower’s ability to develop new fuels and materials that can breed and burn U-238 could enable a TWR prototype to get more energy out of every pound of mined uranium than a conventional light water reactor.

TerraPower’s mission is to develop this nuclear reactor to meet growing global electricity needs. The goal of the TWR design is to greatly reduce proliferation risks and create new, affordable options for converting low-level waste into energy resources.

Looking to the Future

The TWR technology will evolve as we proceed with materials testing and a prototype reactor. Our studies show that future generations of the technology will be capable of running on other forms of fuel–spent light water reactor fuel or recycled TWR fuel.